PHOTODEGRADATION OF SUPRAMEOLECULAR PHOTOCATALYSTS INVESTIGATED BY HPLC

High performance liquid chromatography (HPLC) is a method that significantly enhances the capabilities of standard chromatography techniques.[6,7] In HPLC the eluent/mobile phase is pumped with high pressure through the column/stationary phase by a mechanical pump. Separation of fractions takes place by interaction of the eluted compounds with the stationary phase leading to separation e.g. by polarity or size, depending on the column material. Due to this interactions, different compounds will elute with different speed and have different retention times. Further influences on the elution can be achieved by eluent gradients or changes in the temperature or operating pressure. This way, separation of very similar compounds such as isomers or even enantiomers is possible. Sample collection takes place at the end of the column and fractions are usually detected by optical spectroscopy like an absorption or emission detector. Despite the different retention times of different compounds these spectra can already provide information that can help to identify the specific compound. Combination with other characterisation methods such as mass spectrometry or NMR (for semi-preparative HPLC) is possible and can further help identifying certain fractions. Therefore, HPLC is ideally suited to investigate compounds of similar chemical composition like degradation products of metal complex photocatalysts.